Research Papers: Evaporation, Boiling, and Condensation

Effect of Acoustic Excitation on R134a/Al2O3 Nanolubricant Mixture Boiling on a Reentrant Cavity Surface

[+] Author and Article Information
M. A. Kedzierski

Fellow ASME
National Institute of Standards and Technology,
Gaithersburg, MD 20899
e-mail: MAK@NIST.GOV

S. E. Fick

National Institute of Standards and Technology,
Gaithersburg, MD 20899

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 9, 2014; final manuscript received June 1, 2015; published online July 14, 2015. Assoc. Editor: Sujoy Kumar Saha.This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Heat Transfer 137(11), 111503 (Jul 14, 2015) (9 pages) Paper No: HT-14-1601; doi: 10.1115/1.4030884 History: Received September 09, 2014

This paper quantifies the influence of acoustic excitation of Al2O3 nanoparticles on the pool-boiling performance of R134a/polyolester mixtures on a commercial (Turbo-BII-HP) boiling surface. A nanolubricant with 10 nm diameter Al2O3 nanoparticles at a 5.1% volume fraction in the base polyolester lubricant was mixed with R134a at a 1% mass fraction. The study showed that high-frequency ultrasound at 1 MHz can improve R134a/nanolubricant boiling on a reentrant cavity surface by as much as 44%. This maximum enhancement occurred for an applied power level to the fluid of approximately 6 W and a heat flux of approximately 6.9 kW/m2. Applied power levels larger and smaller than 6 W resulted in smaller boiling heat transfer enhancements. In total, five different applied power levels were studied: 0 W, 4 W, 6 W, 8 W, and 12 W. The largest and smallest enhancement averaged over the tested heat flux range were approximately 12% and 2% for the applied power levels of 6 W and 4 W, respectively. In situ insonation at 1 MHz resulted in an improved dispersion of the nanolubricant on the test surface. An existing pool-boiling model for refrigerant/nanolubricant mixtures was modified to include the effect of acoustic excitation. For heat fluxes greater than 25 kW m−2, the model was within 4.5% of the measured heat flux ratios for mixtures, and the average agreement between measurements and predictions was approximately 1% for all power levels.

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Fig. 1

Schematic of test apparatus

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Fig. 2

Schematic of ultrasonic piezoelectric transducer showing presumed amplitude variations with respect to the boiling surface

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Fig. 3

OFHC copper flat test plate with Turbo-BII-HP surface and thermocouple coordinate system

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Fig. 4

Photograph of Turbo-BII-HP surface

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Fig. 5

TEM image of Al2O3 nanolubricant [25]

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Fig. 6

R134a/5AlO (99/1) mixture boiling curves for Turbo-BII-HP and P = 0 W

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Fig. 7

Effect of extended acoustic excitation on the boiling heat flux of R134a/5AlO (99/1) Turbo-BII-HP

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Fig. 8

R134a/nanolubricant mixtures boiling curves for Turbo-BII-HP for various ultrasonic applied levels

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Fig. 9

Acoustically excited boiling heat flux of R134a/nanolubricant mixtures relative to that without excitation for Turbo-BII-HP

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Fig. 10

Prediction of acoustically excited boiling heat flux of R134a/nanolubricant mixture relative for Turbo-BII-HP

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Fig. 11

Effect of net power on acoustically excited boiling heat flux of a R134a/nanolubricant mixture




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